The previous work relating to the numerical-analytical coupling method for steady-state thermal analysis of the laminated PCB structure is first briefly reviewed. The Fourier-series analytical ...solution of temperature and the finite volume method were linked together for thermally modeling the PCB. For further modeling the PCB with components, thermal-resistance parameters of the components are then used for correlating components’ temperatures with the variable arrays in the coupling equations. For further considering radiation heat transfer between the PCB and the ambient, an iterative method is proposed. The radiation-equivalent heat transfer coefficient for each surface cell and each component can be updated during the iteration. Moreover, for improving the efficiency, the multigrid strategy is integrated in the coupling method for generating discrete cells of three levels in the metal layer and PCB surface region. To testify the iterative method, the model of a simple one-layer structure is compared with that built in COMSOL Multiphysics. The modeling results of the PCB of a phantom DC-DC power supply under radiation heat transfer are also given and discussed, and the modeling accuracy is approximately derived based on Richardson’s extrapolation.
The haze phenomenon in China is becoming increasingly severe. Although some meteorological factors contribute to this phenomenon, it is ultimately linked to economic factors such as the extensive ...development and the unbalanced industrial structure. By using a semi-parametric global vector autoregressive model (SGVAR) and the environmental Kuznets curve, this study takes a spatial correlation perspective to investigate the influence of industrial restructuring on haze pollution and its spatial spillover effects. The empirical analysis is based on China's provincial quarterly panel data between 2001 and 2010. The results show that (1) spatial spillover characterizes China's haze pollution. That is, haze pollution in one area will aggravate haze pollution in surrounding areas; the industrial structure, dominated by heavy industry, will exacerbate haze pollution and further aggravate its spatial spillover. (2) At the regional level, the air pollution spillover effect in eastern China is stronger than that in the central and western (backward) areas. (3) There is an approximate inverse-U-shaped relationship between haze pollution and economic growth in most provinces, except Beijing and Shanghai, where haze pollution is still expected to intensify with economic growth. Therefore, in the formulation of haze pollution control policies, full consideration must be given to the impact of spatial factors, not only to promote the transfer of industrial structures in the eastern region but also to strengthen the promotion and coordination between provinces and regions and, ultimately, control pollution.
Reversed Cherenkov radiation is the exotic electromagnetic radiation that is emitted in the opposite direction of moving charged particles in a left-handed material. Reversed Cherenkov radiation has ...not previously been observed, mainly due to the absence of both suitable all-metal left-handed materials for beam transport and suitable couplers for extracting the reversed Cherenkov radiation signal. In this paper, we develop an all-metal metamaterial, consisting of a square waveguide loaded with complementary electric split ring resonators. We demonstrate that this metamaterial exhibits a left-handed behaviour, and we directly observe the Cherenkov radiation emitted predominantly near the opposite direction to the movement of a single sheet electron beam bunch in the experiment. These observations confirm the reversed behaviour of Cherenkov radiation. The reversed Cherenkov radiation has many possible applications, such as novel vacuum electronic devices, particle detectors, accelerators and new types of plasmonic couplers.
Preparation of stable water‐in‐oil (W/O) high internal phase emulsion (HIPE) containing methyl methacrylate (MMA) monomer as oil phase is a difficult task due to the significant solubility of MMA in ...water. Here, for the first time a fluorinated di‐block copolymer (FDBC) poly (2‐dimethylamino)ethylmethacrylate‐b‐poly (trifluoroethyl methacrylate) (PDMAEMA‐b‐PTFEMA) is proposed to stabilize HIPEs of MMA without the use of any co‐stabilizer or thickening agent. Fluorinated segments in FDBC anchored well at oil/water interface of HIPE, offering high hydrophobicity to the partially hydrophilic MMA monomer and in turn stabilization to MMA‐HIPE. By using fluorinated di‐block copolymer as stabilizer, highly stable HIPEs can be obtained. In addition, highly interconnected porous monoliths were obtained after free radical polymerization, which are highly desirable materials in various practical applications including tissue engineering scaffolds, separation science, bio‐engineering and so on. The as‐prepared MMA‐HIPEs possess high thermal stability without phase separation. The textural characteristics of as‐prepared composites, such as pore size and distribution, can be easily controlled by simply varying the amount of FDBC and/or dispersed phase fraction. Moreover, the influence of di‐block concentration on water uptake (WU) capability of the prepared porous monoliths is explored.
Preparation of porous methyl methacrylate with high internal phase emulsion (HIPE) solely stabilized by fluorinated di‐block copolymer is described. Optical and scanning electron microscope images of HIPE and polyHIPE, are presented.
Summary
Many Actinidia cultivars are characterized by anthocyanin accumulation, specifically in the inner pericarp, but the underlying regulatory mechanism remains elusive. Here we report two ...interacting transcription factors, AcMYB123 and AcbHLH42, that regulate tissue‐specific anthocyanin biosynthesis in the inner pericarp of Actinidia chinensis cv. Hongyang. Through transcriptome profiling analysis we identified five MYB and three bHLH transcription factors that were upregulated in the inner pericarp. We show that the combinatorial action of two of them, AcMYB123 and AcbHLH42, is required for activating promoters of AcANS and AcF3GT1 that encode the dedicated enzymes for anthocyanin biosynthesis. The presence of anthocyanin in the inner pericarp appears to be tightly associated with elevated expression of AcMYB123 and AcbHLH42. RNA interference repression of AcMYB123, AcbHLH42, AcF3GT1 and AcANS in ‘Hongyang’ fruits resulted in significantly reduced anthocyanin biosynthesis. Using both transient assays in Nicotiana tabacum leaves or Actinidia arguta fruits and stable transformation in Arabidopsis, we demonstrate that co‐expression of AcMYB123 and AcbHLH42 is a prerequisite for anthocyanin production by activating transcription of AcF3GT1 and AcANS or the homologous genes. Phylogenetic analysis suggests that AcMYB123 or AcbHLH42 are closely related to TT2 or TT8, respectively, which determines proanthocyanidin biosynthesis in Arabidopsis, and to anthocyanin regulators in monocots rather than regulators in dicots. All these experimental results suggest that AcMYB123 and AcbHLH42 are the components involved in spatiotemporal regulation of anthocyanin biosynthesis specifically in the inner pericarp of kiwifruit.
Significance Statement
AcMYB123 and AcbHLH42 are the components involved in spatiotemporal regulation of anthocyanin biosynthesis specifically in the inner pericarp of kiwifruit.
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The plunging depth of 0.05mm was optimum for joint formation of 0.5mm thick Al-6061 sheet by micro friction stir welding. Increasing rotational velocity from 1500rpm to 2000rpm was ...beneficial to sound surface formation, while the taper pin with three flats owned wider process window than the single taper pin. The minimum ratio of thickness reduction of 2% was attained, which enhanced the area of load bearing. The taper pin with three flats owing to the severe stirring actions resulted in the finer grain size, improving tensile property. The maximum tensile strength by the taper pin with three flats reached 217MPa, equivalent to 90% of base material.
During the past few years, there have been various kinds of content-aware image retargeting operators proposed for image resizing. However, the lack of effective objective retargeting quality ...assessment metrics limits the further development of image retargeting techniques. Different from traditional image quality assessment (IQA) metrics, the quality degradation during image retargeting is caused by artificial retargeting modifications, and the difficulty for image retargeting quality assessment (IRQA) lies in the alternation of the image resolution and content, which makes it impossible to directly evaluate the quality degradation like traditional IQA. In this paper, we interpret the image retargeting in a unified framework of resampling grid generation and forward resampling. We show that the geometric change estimation is an efficient way to clarify the relationship between the images. We formulate the geometric change estimation as a backward registration problem with Markov random field and provide an effective solution. The geometric change aims to provide the evidence about how the original image is resized into the target image. Under the guidance of the geometric change, we develop a novel aspect ratio similarity (ARS) metric to evaluate the visual quality of retargeted images by exploiting the local block changes with a visual importance pooling strategy. Experimental results on the publicly available MIT RetargetMe and CUHK data sets demonstrate that the proposed ARS can predict more accurate visual quality of retargeted images compared with the state-of-the-art IRQA metrics.
Objective image retargeting quality assessment aims to use computational models to predict the retargeted image quality consistent with subjective perception. In this paper, we propose a ...multiple-level feature (MLF)-based quality measure to predict the perceptual quality of retargeted images. We first provide an in-depth analysis on the low-level aspect ratio similarity feature, and then propose a mid-level edge group similarity feature, to better address the shape/structure related distortion. Furthermore, a high-level face block similarity feature is designed to deal with sensitive region deformation. The multiple-level features are complementary as they quantify different aspects of quality degradation in the retargeted image, and the MLF measure learned by regression is used to predict the perceptual quality of retargeted images. Extensive experimental results performed on two public benchmark databases demonstrate that the proposed MLF measure achieves higher quality prediction accuracy than the existing relevant state-of-the-art quality measures.
The design of core-shell structure is considered as a facile approach to obtain polymer composites with excellent dielectric properties and high breakdown strength (Eb). In this work, ...thiol-terminated poly(vinylidene fluoride) (PVDF-SH) and polystyrene (PS-SH) are synthesized by a two-step process. The as-prepared polymers are applied to modify BaTiO3 (BT) nanoparticles. The subsequent morphologies, dielectric properties, and Eb of PVDF-based composites are investigated systematically. PVDF encapsulated BT (PVDF@BT) fillers carries more desirable compatibility with matrix compared with PS encapsulated BT (PS@BT) and raw BT. For instance, the Eb of the 30 vol% PVDF@BT composites slightly decreased from 150.6 to 117 kV/mm for PVDF matrix, as compared to the raw and PS@BT composites, for those the values intensively reduced to 58.5 kV/mm and 107 kV/mm, respectively. It is also observed that PVDF polymer shells play a significant role in the improvement of composites dielectric constant (εr). Moreover, the design of the polymer shell also contributes to the suppression of dielectric loss. The results are of great importance for understanding the effect of polymer shells and fluorinated filler on composite properties. This study provides a strategy for preparing composites with high εr while maintaining high Eb for the next generation of dielectric capacitors.
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•Ferroelectric polymer poly(vinylidene fluoride) is used simultaneously as a matrix and BaTiO3 modifier.•The breakdown strength of PVDF@BT/PVDF is 100% larger than that of BT/PVDF at 30 vol% filler loading.•15% increase in dielectric constant is observed in PVDF@BT/PVDF as compared to PS@BT/PVDF at 30% filler loading.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the ongoing coronavirus disease 2019 pandemic. How SARS-CoV-2 regulates cellular responses to escape clearance by host cells is ...unknown. Autophagy is an intracellular lysosomal degradation pathway for the clearance of various cargoes, including viruses. Here, we systematically screened 28 viral proteins of SARS-CoV-2 and identified that ORF3a strongly inhibited autophagic flux by blocking the fusion of autophagosomes with lysosomes. ORF3a colocalized with lysosomes and interacted with VPS39, a component of the homotypic fusion and protein sorting (HOPS) complex. The ORF3a-VPS39 interaction prohibited the binding of HOPS with RAB7, which prevented the assembly of fusion machinery, leading to the accumulation of unfused autophagosomes. These results indicated the potential mechanism by which SARS-CoV-2 escapes degradation; that is, the virus interferes with autophagosome-lysosome fusion. Furthermore, our findings will facilitate strategies targeting autophagy for conferring potential protection against the spread of SARS-CoV-2.
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